The present invention relates to a method of manufacturing a magnetic head for a magnetic disk drive unit, etc., and more precisely to a method of manufacturing a magnetic head in which a side face of a ceramic bar member, which includes magnetic head elements, is lapped so as to make the magnetic head elements have prescribed characteristics.
Magnetic head elements used in magnetic disk drive units, etc. have sensing sections, which are formed by forming magnetic layers, non-magnetic layers, etc. on a wafer-shaped ceramic substrate, and terminals connected thereto. Sliders, which will be respectively assembled in magnetic heads and each of which includes a magnetic head element, are formed by dividing the wafer into pieces.
The magnetic head elements are formed by the steps of forming the sensing sections and terminals in the substrate dividing the wafer into thin bar-shaped members 10 (see FIG. 4); and lapping a side face of the bar-shaped member (work piece). The bar-shaped member 10 is made by cutting the wafer, and tens of the magnetic head elements 12 are arranged therein. A general magnetic head element 12 is shown in FIG. 5. In the drawing, a symbol 14 stands for the sensing section, and symbols 16 stand for the terminals. The sensing section 14 made of a magnetic resistance element. Symbols h, t, w respectively stand for height, thickness and width of the sensing section 14.
In the bar-shaped member 10, the magnetic head elements 12 are arranged, and in each magnetic head element 12 the sensing section 14 is headed to one side face of the bar-shaped member 10. A purpose of lapping the side face of the bar-shaped member is to adjust the height (h) of the sensing sections 14 of the magnetic head elements 12 and to adjust resistance of the magnetic head elements 12 within a prescribed range. The height of the magnetic head elements 12 affects the life span of the elements, and the elements cannot have prescribed characteristics if their resistance are outside of the prescribed range.
In the case of adjusting the height of the sensing sections 14 of the magnetic head elements 12 by lapping the bar-shaped member 10, it is difficult to control the lapping action because the bar-shaped member 10 is very small. In a conventional method of lapping the bar-shaped member, ELG (Electro Lapping Guide) elements are employed.
Record density of the magnetic head elements, e.g., MR head, GMR head, becomes higher and higher. To make the record density higher and to gain higher output power, the magnetic head elements should be thinner and the sensing sections should be lower and narrower. Therefore, if products are manufactured by the conventional method, in which amount of lapping the magnetic head elements is indirectly controlled by using the ELG elements, the products cannot have prescribed accuracy.
To control size of the magnetic head elements by using the ELG elements, positional relationship between the ELG elements and the magnetic head elements must be precisely known. Since the bar-shaped member must be broken and optically measured in order to correctly know the positional relationship between the ELG elements and the magnetic head elements, the positional relationship is known on the basis of the average of sampled data. By employing the average relationship, a difference must occur between the actual relationship between the ELG elements and the magnetic head elements and the average relationship there between. And, resistivity of layers of the ELG elements and the magnetic head elements, the resistance of the terminals, etc. are not fixed, so they affect the accuracy of the products.
Besides the method of employing the ELG elements, a method of adjusting the size and the resistance of the magnetic head elements by monitoring the elements was proposed. However, it is almost impossible to monitor the resistance of the magnetic head elements and control the height of the sensing sections because the width of the magnetic head elements is narrow and the rate of changing the resistance, with respect to the height thereof, is low.
Resistance between the sensing sections and the terminals is greater than that of the sensing sections, so that it is difficult to control the height. Further, the magnetic head elements are easily damaged by static electricity, so they are apt to be damaged by connecting wires for monitoring the elements.
The present invention has been invented to solve the above described problems, and an object of the invention is to provide a method of manufacturing a magnetic head, which is capable of precisely controlling the amount of lapping the bar-shaped member and precisely machining the fine magnetic head elements with higher yield rate.
The method of the present invention comprises the steps of: forming a plurality of layers, which are made from prescribed materials, on a substrate; and forming a plurality of magnetic head elements on the substrate, characterized by the step of forming a first ELG element, whose size in a prescribed direction is bigger than that of the magnetic head elements, and a second ELG element, whose shape is equal to that of the magnetic head elements, on the substrate.
The method may further comprise the steps of: forming a work piece having a prescribed size by cutting a wafer, which includes the substrate and the magnetic head elements, first and second ELG elements formed thereon; lapping the work piece, while monitoring resistance of the first ELG element, until the resistance of the first ELG element reaches a prescribed value; and adjusting the amount of lapping the work piece on the basis of the resistance of the second ELG element.
In the method, a plurality of the first or second ELG elements may be formed. The resistance of the first or second ELG elements are statistically processed, and force pressing the work piece may be adjusted so as to determine the resistance of the first ELG elements or second ELG elements within a prescribed range. With this structure, lapping the bar-shaped member can be correctly controlled when the magnetic head elements are made by lapping the bar-shaped member, so that the magnetic head member can have the prescribed height and prescribed resistance.
Thus, characteristics of the magnetic head elements can be even, and the yield rate of manufacturing can be improved. The method can be effectively applied to the case of making fine elements, e.g., MR head, GMR head. Further, in comparison with the method of monitoring the magnetic head elements only, lapping time can be shorter.
In the method, if a groove is formed in the second ELG element, the second ELG element can be removed when the bar-shaped member is divided.
In the method, if a part of the magnetic head elements acts as the second ELG element, the magnetic head element can be used as a dummy of the second ELG element.